Terminal structure



Oct. 24, 1939. C, C, ABBOTT Y 2,177,509/

TERMINAL STRUCTURE Original Filed July 29. 1.936

70 f@ I 9 Inventor:

\\\\\\\\\\\` Charles c. Abbott,

Attorney.

Patented Oct. 24, 1939 uNiTED STATES TERLIINAL STRUUIUBE charles c. Abbotemttsnela, Mass., assigner u General Electric Company, a. corporation ofA New vYork Original application July 29, 1936, Serial No. 93,213. Divided and this application April 28,

1937, Serial No. 139,448

4 Claims. (131. 20L-67) This invention relates to'terminal structures, more particularly to terminal structures for electric heaters, and it has for its object the provision of an improved method for sealing the terminals of the heater. I

Although not limited thereto, this invention has particular application to electric heaters of the incased or sheathed type wherein a resistance conductor embedded in an electrically insulating material is inclosed by an outer metallic protective casing, such as described and claimed in my U. S. Patent No. 1,367,341, dated February 1, 1921; and it contemplates the provision of an improved method for securing the terminal housing to the heater and also to the supply lead, in such manner as to prevent the admission to the ter-V minal of fluids such as water, oil, gas, etc.

This application is a division of my copending application, Serial No. 93,213, led July 29, 1936.

For a more complete understanding of this invention, reference should be had to the accompanying drawing in which Fig 1 is a plan view of a sheathed electric heater embodying this invention; Fig. 2 is an enlarged fragmentary View mainly in section illustrating a portion of the heater of Fig. 1; Fig. 3 is an enlarged fragmentary lview mainly in section illustrating aterminal structure of modified form arranged in accordance with this invention; Fig. 4 is a fragmentary view mainly in section illustrating a` modied form of this invention; Fig. 5 is a fragmentary view similar to Fig. 4, but illustrating the means of Fig. 4 as used to splice two heating units together; and Fig. 6 is a view illustrating a heater similar to that shown in Fig. 4, but of somewhat diierent form.

Referring to Figs. 1 and 2 of the drawing, this invention has been shown in one form as applied to a dam gate armature heater comprising a pair of sheathed heating elements Ill and II arranged in substantially parallel relation, as shown in Fig. l. Each heating element I0, II preferably will be of the type described and claimed in my abovementioned U.'S. Patent No. 1,367,341. each of the heating elements Ill, 'II comprises a. sinuous resistance conductor I2 (Fig. 2) arranged 'centraly of a metallic sheath I3 and supported in spaced relation with reference to thesheath by a highly compacted Vlayer of heat refractory, electrically insulating material Il, such as powdered magnesium oxide. The left-hand ends of the heaters I0 and II, as viewed in Fig. 1, are connected together by means of a suitable plug I5 in which the ends of the sheathed heaters are received, and which has suitable means (not As shown,

shown) for electrically interconnecting the resistance conductors I2 of the two heaters. 'I'he vtwo heaters IIl and II are rigidly secured together in spaced relation and at spaced intervals by suitable spacers I6. And, as shown, the heaters at their ends opposite the connector member I5 are spaced apart somewhat farther than the rest of the heaters. To these ends is secured a plate member I1 that constitutes a cover when the heater is applied to the dam gate armature.A It will be understood that the heaters are inserted in suitable casings or channels (not shown) and that the cover plate is used to close the casings.

T'he right-hand ends of the heaters, as viewed in Figs- 1 and 2, constitute the terminal ends, and arranged within and projecting from each of these ends of the sheaths is a suitable terminal member I8 connected to the resistance conductor I2, as shown in Fig. 2. A suitable fluid impervious seal is provided between the terminal and the sheath comprising a layer of glass I9 adhering to the terminal and to the sheath, and an electric insulator 20 inserted in the glass, as clearly shown in Fig. 2. The specic seal between the terminal and the sheath is arranged substantially in accordance with the seal described and claimed in the United States patent to R. J. Sutton No.

1,922,787, dated February 26, 1935.

The terminal structure for the heater further comprises a suitable metallic tubular terminal housing 2l attached to the terminal end of the sheath and projecting therefrom in alignment with the sheath, as clearly shownin Figs. 1 and 2.

As shown in Fig. 2, the terminal housing 2| has a threaded connection 22 with the end of the sheath and is additionally secured to the sheath by means 'of a suitable brared or soldered connection 23.

This brazed connection is made by forming an annular recess 2l inthe end of the housing 2| around the sheath, iilling this recess with a brazing material 24a, and brazing this material to the housing and sheath to substantially integrally unite -these members. formed while the annular space between the housing 2| and the sheath is vented through a suitable aperture 25 provided inthe terminal housing for this purpose. This permits the air within the annular space to vent itself when the sheath and housing are heated due to the brazing operation. I have found this to be of material sheathed electric heater. If this vent opening is not provided to permit the air to escape, I have discovered that microscopic air holes are found The brazed joint will beY 'importance in securing a terminal housing to a in the brazed section due to the trapped air tending to escape through the brazing material while in a highly heated liquid state, and when the temperatures of the heater and housing are elevated due to the brazing operation. Q'I'hese microscopic air holes later on in the operation of the heater permit moisture to enter the terminal housing. This moisture weakens materially the electrical insulation in the terminal housing and ultimately will cause failure. After the brazing operation has been completed a suitable metallic plug 26 is forced into the aperture 25 and then the exposed end of the plug is brazed to the walls of the housing.

An electrical supply lead 21 enters the housing 2 i. 'I'his lead comprises an electrical supply conductor 26 which is covered by a yielding electrically insulating covering or layer 19 formed of any suitable material, such as rubber. The main portion of thev covering 29 in turn is covered by a suitable protective Acasing 30 formed of any suitable metallic material, such as lead.

Arranged within the chamber or housing 2i around the terminal and connector members and the inner portion of the lead 21 is a suitable electrically insulating sleeve Il. This Amember may be formed of any suitable electrically insulating material, such as baked lava. Arranged on the outer end of the sleeve 3l are a plurality of yieldable sealing members 32 yieldingly engaging the covering 29, and separated from each other by means o! a plurality of metallic washers 33. The yieldable members I32 are forced inwardly by means of a loading plug 34.l The arrangement of the sleeve 3l, the washers 32 and 33 andthe loading plug 34 is as described and claimed in my above-mentioned copending application Serial No. 93,213.

In Fig. 3, I have illustrated a terminal structure of modiiled form and arranged in accordance with this invention. In this case, the lead I6 enters the terminal housing 36 where it is connected with the terminal 31 of the heater in the same manner as in the first form described. In this case also, the terminal housing 36 is secured to the sheath 36 of the heater in the same manner as in the ilrst form, but it is also directly connected with the metallic outer casing 35a of the lead so asto provide a uid impervious joint atthis point. For this purpose, the housing is directly connected with the loading plug 39 by means of a soldered joint. As shown, the outer section of the plug has s'uch a diameter that when it is turned inwardly; as shown in Fig. 3, an

annular space 40 is left between this section and the housing 36. Within this space is provided a suitable soldering material 4| which is soldered both to the housing and to the plug to provide a fluid impervious joint between these members. 'I'he outer section of the plug 39 in turn is secured to the metallic casing 36a of the lead by means of a soldered joint 42. The diameter of this outer section of the plug is larger than the lead,

and is flared outwardly, as clearly shown in Fig. 3, to provide a space for the reception of the soldering material 42. When the soldered joint 42 is formed, the annular space between the lead sheath 35a and the plug is vented to the atmosphere through an opening 43. 'I'his vent opening. as, before, is subsequently closed by means of a pin 44 which is soldered to the plug.

The lead 36 is reentorced by a rubber sleeve 45 which is secured by taping 46, as described in my copendingapplication, Serial No. 93,213.

In Fig. 4, there is illustrated a modied form of connection between the terminal housing and the sheath of the heater. As shown in this case, the terminal housing 4l is relatively long and has a close iit with the outer wall of the sheath 4B. The housing 41 is provided with a pair of spaced annular passageways 49 about the sheath, each passageway opening to the exterior of the sheath through a duct to a passageway 50. The annular passageways 49 are lled with brazing material 5I through the passageways 5D to braze the terminal housing to the sheath. A vent hole 52 is provided between the passageways 49 to vent the annular space between the terminal housing and the sheath during the brazing operation. 'I'he hole 52 is subsequently closed by a pin 53 which is brazed over to secure it to the housing.

In Fig. 5, there areillustrated two sheathed heating elements 54 and 55 spliced together by a combined connector member and terminal housing 56. The housing 56 is brazed to each heating unit in the manner previously described in connection with Fig. 4. Thus, the terminal housing is provided with spaced annular passageways 5l surrounding each heating unit 54, 55 adjacent the end of the heater, as shown in Fig. 5. A brazing material 58 is inserted in these passageways and is brazed to the respective heater and housing while the annular space between the heater and the housing is vented through a passageway 59 which is subsequently closed by a pin 6ii,brazed to the housing. If it be desired, two vent openings 59 may be provided for each heater, as shown in Fig. 5.

vThe terminals 6| of the two heaters are secured together by a connector 62 threaded on the terminals asshown. Washers 63.formed of any suitable electrically insulating material, such as mica, are placed on the terminals between the 'ends of the heating unit and the connector 62. A sleeve 64 formed of a similar electrically insulating material is placed around the connector, as shown. The sheath of each unit is provided with a series oi' spaced circular groves 65 to prevent uxes used in the brazing operation from working along the sheath to the mica washers 63. Preferably, the annular space-between the terminal housing and the sheath at the sections where the grooves 65 are formed will also be provided With vents 66 opening to the atmosphere during the brazing operation, and subsequently closed by pins or plugs 61 brazed to the housing.

In Fig. 6, there is illustrated a heater 68 having a terminal housing 6! secured .to it by brazed joints ,1li in the same manner as the terminal housings of Figs. 4 and 5 are secured to their heaters, but in this case the terminal housing is arranged at a predetermined angle to the main body of the heater. The housing in this case is provided with a reduced extension 1I, and the angular relation between the housing 69 and the heater is applied by bending the housing at a point in the reduced extension beyond the brazed section 1U, as shown. Bending the housing at this section causes it to grip the heater firmly and obviates the possibility of strains being set up in the brazed joints 1li.

While I have shown particular embodiments of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modiiications as fall within the trafo spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a terminal structure for a sheathed electric heater, the method oi securing a terminal housing to the end of said heater which comprises forming said housing with a passageway 'to receive the sheath of said heater, forming a channel in said housing surroundingv said passageway and sheath and opening to the vexterior of said housing, forming an opening in said housing adjacent said channel to vent said passageway to the exterior of said housing, inserting brazing' material in said channel and heating it to braze ceive the sheath of said heater, forming a plurality of channels in said housing surrounding said passageway and sheath and opening to the exterior of said housing, forming a vent in said housing between said channels and connecting the passageway with the exterior of the housing, in-

serting brazing material in said channels and,

brazing said housing to said sheath., inserting a pin into said vent to close it and then brazing said pin to said housing.

3. In a terminal structure for a sheathed electric heater, the method of securing a terminal housing to the heater which consists in threading the terminal housing onto the end of the sheath. providing an annular recess in the inner wall of the housing about the outer wall of the sheath and opening to the exterior of said housing, providing in said housing a vent hole adjacent said annular recess and connecting the annular space between the outer wall of the sheath and the inner wall of the housing with the exterior of the housing, inserting brazing material in said annular recess and heating it to braze the housing to the sheath while' said opening allows the vescape of air from said annular space,-and thensubsequently inserting a pin in said vent hole to fclose it, and brazing the pin tothe housing.

4. In a terminal structure for aesheathed electric heater, the method of securing a terminal housing to theheater which consists in inserting the terminal end of the heater into the housing, providing an annularchannel in said housing arranged to vsurround said sheath and opening to the exterior of said housing, providing in said sheath' a plurality of grooves between said channel and the end o! the sheath, providing 'in said housing a vent hole on one side oi.' said channel and opposite the section of said sheath where said grooves are provided and a second vent hole on the other side of 'said channel, then filling said channel with brazing material and heating it to braze the housing to the sheath while said vent holes are open to allow the escapey of air from the space between said heater and housing and subsequently sealing said vent holes.

CHARmsaABBOTr. 

